Berlin: German football club Borussia Dortmund's midfielder Sebastian Kehl will be out of action for four weeks due to a left shoulder injury, the club has confirmed in an official statement.

The veteran defensive midfielder suffered a separated shoulder after a collision with team-mate Mats Hummels inside the penalty box during a 1-0 victory over Romanian club FC Steaua Bucuresti in a friendly match Tuesday, reports Xinhua.

Kehl's injury is a setback for coach Juergen Klopp, who has no defensive midfielder at his disposal for the Jan 31 German League match against third placed Bayer Leverkusen, which is the opening game of the second half of the season.

Dortmund currently occupy the penultimate position of the Bundesliga standings with only 15 points from 17 matches.